Question: Simplify the following expression: ${-(2a+6)+3(1+3a)}$
Answer: The minus sign in front of the parentheses means we multiply each term inside the first parentheses by ${-1}$ $ {-1(}\gray{2a+6}{)} + 3(1+3a) $ $ {-2a-6} + 3(1+3a) $ Distribute the ${3}$ into the parentheses: $ -2a-6 + {3(}\gray{1+3a}{)} $ $ -2a-6 + {3+9a} $ Rewrite the expression to group the ${a}$ terms and numeric terms: $ {-2a + 9a} {-6 + 3}$ Combine the ${a}$ terms: $ {7a} {-6 + 3}$ Combine the numeric terms: $ {7a} {-3}$ The simplified expression is $7a-3$